Settings: Remove advancedToggleExpanded/hasExpandedSection_ logic.

This logic seems to be oblolete and most likely a leftover from back
when Settings would show all sections concurrently, as well as when
subpage opening/closing would animate.

Moreover removed showAdvancedPage_() logic completely as it also does
not seem to be adding any benefit, nor being necessary from a
functionality perspective.

Bug: None
Change-Id: I47c4abbaad9ff4ce392319a74860b26a7cceb0b2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5011437
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1223160}